The present invention relates to a method of and to an apparatus for forming a rod-like filler from several fibrous materials. More particularly, the invention relates to improvements in methods of and in apparatus for making rod-like fillers from smokable fibrous material and/or from fibrous material which, though not smokable, can be used in rod-shaped articles of the tobacco processing industry. Typical examples of rod-like fillers which can be formed in accordance with the method and in the apparatus of the present invention are fillers of cigarette rods which are wrapped and severed to yield plain cigarettes of unit length or multiple unit length.
Commonly owned U.S. Pat. No. 4,009,722 to Wahle et al. discloses a method of and a machine for the making of a composite stream of fibrous material which can be converted into the filler of a cigarette rod. Reference may also be had to commonly owned German Offenlegungsschrift No. 34 22 434 as well as to the commonly owned German Offenlegungsschrift No. 34 01 372. The methods and apparatus which are disclosed in such earlier publications are quite satisfactory. However, it has been found that the zones of transition from fibrous material of one type to fibrous material of another type (e.g., from highquality tobacco which is adjacent to the lighted end of a cigarette to lower-quality tobacco at the mouthpiece end of a cigarette) are not entirely satisfactory. Thus, the texture of the composite stream (and of the rod-like filler which is obtained from such stream) in the regions of abutment of batches consisting of a first fibrous material against batches or analogous accumulations consisting of a second fibrous material is not as satisfactory as within a batch or within an accumulation. In many instances, the just mentioned regions include cavities or unsatisfactorily filled pockets in the composite stream. The presence of cavities is detrimental to the quality of the composite rod, to the quality of the rod-like filler, and to the quality as well as to the appearance of the rod-shaped smokers' products which are obtained as a result of draping the filler into a web of cigarette paper or other suitable wrapping material and subdividing the wrapped filler into rod-shaped sections of unit length or multiple unit length.